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Water Quality Analysis

More than 180 bore water samples were collected in a project to address the impact of water quality on spray efficiency in the Macquarie Valley.

Sustainable Soils Management (SSM) in Warren was contracted to deliver this project. All property owners who provided samples should have received a summary report on their water quality, as well as insights to some of the issues affecting the valley.

Summary findings

SOS member results facilitated the collection of 180 mostly bore water samples from an area west of the Newell Highway and north and east of the Bogan River. Bores in this area extract water from either the Great Artesian Basin aquifer or from unconsolidated (not rock) alluvial aquifers.

The water was assessed for suitability as a carrier for 25 herbicides and three insecticides that were selected as widely used by SOS chemical resellers. The four water properties assessed were:

  1. pH
  2. hardness
  3. bicarbonate concentration
  4. salinity.


Although 78% of water samples were more alkaline than desired, the water can be acidified before adding sensitive pesticides. A similar approach can be used to soften the 20% of samples with hard water.

Bicarbonate concentration was higher than desired for 80% of samples, with half of all samples having bicarbonate concentration more than double the critical value.

Three of the pesticides assessed were rated as sensitive to this water. The water can be amended in two of three cases, but not for 2, 4-D and MCPA amine.

Water salinity was desirably low in 68% of samples and less than 50% above the critical value for most of the remainder.

Three pesticides were rated as sensitive for the saline water. Less saline water should be used with these pesticides.

In general, the water sampled was alkaline, with low to moderate salinity, was generally soft, but often had high carbonate concentration. Water sampled from bores in the confined Great Artesian Basin aquifer had very consistent properties, but water chemistry from shallower bores was much more variable.

In general, water northeast of a line from Coonamble through to Gilgandra and Warren to Nyngan was more alkaline, had higher bicarbonate concentration and contained few bores with hard and saline water than bores south and east of this line.

Further work recommended is to test the effect of 2, 4-D and MCPA amine. 

Download the full report (PDF 1.6MB)

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